This application is based on Application No. 2000-317930, filed in Japan on Oct. 18, 2000, the contents of which are hereby incorporated by reference.
The present invention generally relates to a cylinder identifying system for an internal combustion engine mounted on an automobile or a motor vehicle. More particularly, the present invention is concerned with a cylinder identifying system for an internal combustion engine which system is designed for identifying discriminatively individual cylinders of the internal combustion engine within a short time upon starting of operation of the engine to thereby allow a fuel injection control and an ignition control for the engine to be speedily carried out on a cylinder-by-cylinder basis.
As the hitherto known or conventional cylinder identifying system of the sort mentioned above, there can be mentioned the one which is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 146992/1994 (JP-A-6-146992). In the cylinder identifying system described in this publication, a crank angle pulse signal generated in synchronism with rotation of a crank shaft of the internal combustion engine and a cam pulse signal generated in synchronism with rotation of a cam shaft which is operatively coupled to the crank shaft and rotated at a speed ratio of xc2xd relative to that of the crank shaft are employed for detecting the angle of rotation or angular position of the crank shaft on the basis of which engine operation controls such as a fuel injection control, an ignition control, etc. are performed for the individual cylinders of the engine.
For generating the crank angle pulse signal, a crank angle sensor is provided which is constituted by a ring gear (or toothed wheel) mounted in a coaxial relation with the crank shaft and having an outer periphery formed with projections or teeth and an electromagnetic pickup device disposed in opposition to the outer periphery of the ring gear for generating pulses in response to the individual projections or teeth, respectively. The crank angle pulse signal is derived from the output signal of the electromagnetic pickup device and includes sequentially a series of pulse trains, wherein each pulse train corresponds to a predetermined angle of rotation of the crank shaft or a predetermined angular range delimited by a reference position.
On the other hand, the pulse generator for generating the cam pulse signal is so arranged that the numbers of pulses contained in the cam pulse signals, respectively, differ from one another for the crank angle pulse signals SGT generated successively each over a predetermined crank angle range corresponding to given one of the engine cylinders. Thus, on the basis of combination of the numbers of pulses contained in the cam pulse signals generated within a preceding range (during a preceding period, to say in another way) and within a current range (during a current period), it is certainly possible to identify the individual cylinder sets as well as particular or specific position(s) in the crank angle pulse signal.
However, in the conventional cylinder identifying system for the internal combustion engine, the combinations of the pulse numbers generated at the specific positions are limited to three values, i.e., xe2x80x9c0xe2x80x9d, xe2x80x9c1xe2x80x9d and xe2x80x9c2xe2x80x9d. Accordingly, in the case of a six-cylinder engine, it is impossible to identify discriminatively any given cylinder on the basis of only the combination of the numbers of pulses generated during two periods (or over two ranges), respectively.
Further, since the specific position and the cylinders are determined discriminatively on the basis of the combination of the numbers of pulses generated during the preceding period and the current period, respectively, the cylinder identification is rendered impossible in the case where the end point of the current period does not coincide with the specific position.
By way of example, in the case of the four-cylinder engine, the range of crank angles corresponding or equivalent to one period is set to be 90xc2x0 CA (i.e., 90 degrees in terms of the crank angle or CA in short). Consequently, the cylinder identification processing can be completed within a period corresponding to rotation of the engine for 180xc2x0 CA at the shortest although it depends on the crank angle at which the engine was stopped in the preceding operation. However, there will arise such situation that the cylinder identification can not be completed until the engine has rotated over 360xc2x0 CA at maximum, which of course depends on the crank angle at which the engine was stopped in the preceding operation. In the latter case, starting of the engine operation from the stopped state requires a lot of time, needless to say.
Another cylinder identifying system for the internal combustion engine is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 311146/1999 (JP-A-11-311146). In this known cylinder identifying system, a crank angle pulse signal (POS) including pulse trains each having a duration or a period which corresponds to a predetermined crank angle range (10xc2x0 CA) and having a reference position which corresponds to a tooth absent or dropout location in an outer peripheral projection or tooth array of a ring gear, an angle reference signal (REF) indicating an angle reference differing from the reference position mentioned above, and a cam pulse signal (CAM).
In this cylinder identifying system known heretofore, the cam pulse signal generating unit is so arranged that the numbers of pulses generated during successive subperiods, respectively, which are defined by dividing a corresponding crank angle period for each engine cylinder differ from each other.
In the system mentioned above, an electronic control unit which may be constituted by a microcomputer or the like is so designed as to respond to detection of the angle reference signal REF to thereby divide a range or period defined between a detected start point (leading edge) and an end point (trailing edge) of the angle reference signal REF into a plurality of subperiods (e.g. two subperiods).
The durations of the subperiods can be measured with the crank angle pulse signal POS. On the other hand, an array of projections or teeth formed on and along the outer periphery of a rotatable plate mounted coaxially with the cam shaft is previously so arranged that the cam pulse signals CAM generated during the subperiods, respectively, differ from each other in respect to the pulse number.
More specifically, the numbers of pulses of the cam pulse signals CAM generated during the subperiods are previously set to two different values (e.g. xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d), respectively, wherein the cylinder identification can be realized on the basis of combination of the numbers of the cam pulses generated during the subperiods each extending from a given angle reference signal REF to a succeeding angle reference signal REF.
Also in this case, a period extending between the angle reference signals REF is divided into a plurality of subperiods after detection of the angle reference signals REF and then the cylinder identification is carried out on the basis of combination of the numbers of pulses generated during the plural subperiods, respectively. Thus, the cylinder identification can be started only after the generation of the angle reference signals REF.
Such being the circumstances, also in the cylinder identifying system disclosed in Japanese Unexamined Patent Application Publication No. 311146/1999, one period which corresponds to revolution of the engine for 180xc2x0 CA is required for completing the cylinder identification processing at the shortest although it depends on the crank angle at which the engine was stopped in the preceding operation thereof, similarly to the case of the cylinder identifying system disclosed in Japanese Unexamined Patent Application Publication No. 146992/1994. In the worst case, the cylinder identification can not be completed until the engine has been rotated over 360xc2x0 CA, which means, needless to say, that a lot of delay time will be involved for starting the engine operation from the stationary state.
Further, since the numbers of the pulses generated during the subperiods, respectively, are set at different values xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d, there may arise such situation in the case of the four-cylinder engine that the numbers of pulses generated in both the preceding and succeeding subperiods are xe2x80x9c0xe2x80x9d and xe2x80x9c0xe2x80x9d, respectively. In this conjunction, it is noted that similar situation will take place upon occurrence of a fault such as wire breakage. In that case, no cam pulse signal is generated. In other words, distinction from the state in which no cam pulse signal is generated due to a fault is rendered impossible, incurring thus a problem in respect to the fail-safe function.
As can now be appreciated from the foregoing description, in the conventional cylinder identifying system disclosed, for example, in Japanese Unexamined Patent Application Publication No. 146992/1994, the specific or particular position is determined on the basis of the combination of the numbers of pulses of the cam pulse signal generated during predetermined time durations or periods. However, since the number of the combinations of the pulse numbers generated at the specific positions is smaller than the number of the cylinders, it is impossible to identify any given specific cylinder on the basis of only the combination of the numbers of the pulses generated during two discrete periods in the case of a six-cylinder internal combustion engine, giving rise to a problem.
Further, in case the end point of the current period does not coincide with the specific position, it is impossible to perform the cylinder identification on the basis of the combination of the numbers of the generated pulses of the cam pulse signal. As a consequence, the cylinder identification processing can not be completed until the engine has rotated for 360xc2x0 CA at maximum although it depends on the crank angle at which the engine was stopped in the preceding operation, incurring thus a problem that a remarkable time delay will be involved for starting again the engine operation.
On the other hand, in the case of the cylinder identifying system disclosed in Japanese Unexamined Patent Application Publication No. 311146/1999, the cylinder identification is performed on the basis of combination of the numbers of pulses of the cam pulse signal CAM generated during a plurality of subperiods defined by dividing correspondingly the period of the angle reference signal REF, and thus the cylinder identification processing is started after generation of the angle reference signal REF. Consequently, there also arises the problem that the cylinder identification processing can not be completed until the engine has rotated 360xc2x0 CA at maximum although it depends on the crank angle at which the engine was stopped in the preceding operation, as a result of which a lot of time is taken for starting again the engine operation.
Furthermore, since the numbers of pulses generated during the subperiods, respectively, are set to two different values, such problem is incurred that when the number of pulses generated in both the subperiods of the cylinder identification period are xe2x80x9c0xe2x80x9d and xe2x80x9c0xe2x80x9d, distinction from the state where no cam pulse signal is outputted due to occurrence of a fault such as wire breakage is rendered impossible, giving rise to a problem in respect to the failsafe performance.
In the light of the state of the art described above, it is an object of the present invention to provide a cylinder identifying system for an internal combustion engine which system is capable of performing the cylinder identification within a smaller angular range of engine rotation and hence within a shortened time to thereby enable the fuel injection control and the ignition control for each engine cylinder to be speedily carried out upon engine starting operation.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention a cylinder identifying system for an internal combustion engine, which system includes a crank angle signal detecting means for generating a crank angle pulse signal composed of pulse trains each containing a reference position in synchronism with rotation of a crank shaft of the internal combustion engine, a cam shaft rotating at a speed corresponding to one half of that of the crank shaft, a cam signal detecting means for generating a cam pulse signal including specific pulses identifying individual cylinders, respectively, of the internal combustion engine in synchronism with rotation of the cam shaft, and a cylinder identifying means for identifying the individual cylinders, respectively, of the internal combustion engine on the basis of the crank angle pulse signal and the cam pulse signal. In the cylinder identifying system mentioned above, the cylinder identifying means is comprised of a pulse signal number storage means for dividing an ignition control period for each of the individual cylinders into a plurality of subperiods for thereby counting for storage signal numbers of the specific pulses generated during the plural subperiods, respectively, and a subperiod discriminating means for determining discriminatively a sequential order of the plural subperiods on the basis of combinations of the signal numbers of the specific pulses generated during the plural subperiods, respectively. The combinations of the signal numbers of the specific pulses generated during the plural subperiods, respectively, differ from one to another correspondingly to the plural subperiods in dependence on start points of the plural subperiods, respectively. The cylinder identifying means is so designed as to identify the individual cylinders on the basis of results of the discriminative determination of the subperiods performed by the subperiod discriminating means independently of the start points of the plural subperiods.
By virtue of the arrangement described above, there is provided for an internal combustion engine the cylinder identifying system capable of performing the cylinder identification within a smaller angular range of engine rotation and hence within a shortened time for thereby allowing the fuel injection control and the ignition control for each engine cylinder to be speedily carried out upon engine starting operation.
In a preferred mode for carrying out the invention, the pulse signal number storage means may be so designed as to count for storage the signal number of the cam pulse signal and the number of pulses of the crank angle pulse signal, respectively, from the start of operation of the internal combustion engine. The cylinder identifying means may be constituted by a pulse signal sequential order storage means for storing therein temporal relations between the pulse trains of the crank angle pulse signal and the specific pulses of the cam pulse signal, and a reference position detecting means for detecting the reference position from the crank angle pulse signal, wherein when it is decided that the crank angle pulse signal has been detected since a start point of a preceding, subperiod at the latest on the basis of the number of pulses of the crank angle pulse signal which have been stored up to the reference position, the cylinder identifying means identifies the individual cylinders on the basis of the signal number of the cam pulse signal(s) generated during the preceding subperiod.
In another preferred mode for carrying out the invention, the cylinder identifying means may be so arranged that when it is decided after detection of the reference position that the crank angle pulse signal has been detected since the start point of the current subperiod at the latest on the basis of the pulse number of the crank angle pulse signal stored up to a time point at which an end point of the current subperiod including the reference position is detected, the cylinder identifying means identifies the individual cylinders on the basis of the signal number of the cam pulse signal(s) generated during the current subperiod.
In yet another mode for carrying out the invention, the cylinder identifying means may preferably be so implemented that when it is decided on the basis of the pulse number of the crank angle pulse signal stored up to a subperiod end point of the plural subperiods that the crank angle pulse signal has been detected since the start point of the preceding subperiod at the latest, the cylinder identifying means then identifies the individual cylinders on the basis of combination of the signal number of the cam pulse signal(s) generated during the preceding subperiod and the signal number of the cam pulse signal(s) generated during the current subperiod.
Owing to the arrangements of the cylinder identifying system described above, the fuel injection control and the ignition control can be speedily carried out for the individual engine cylinders upon engine starting operation.
In still another mode for carrying out the present invention, such arrangement should preferably by adopted that the combinations of the signal numbers of the cam pulse signals generated during the plural subperiods includes no combination of only xe2x80x9c0sxe2x80x9d which indicates absence of output.
With the arrangement described above, there can be realized the cylinder identifying system which can ensure a fail-safe function described later on.
In a further mode for carrying out the present invention which is applied to a four-cylinder internal combustion engine in which the ignition control period for each of the cylinders is so set as to correspond to a crank angle of 180xc2x0, the plural subperiods should preferably be comprised of a first subperiod and a second subperiod, wherein numbers of the specific pulses contained in the cam pulse signal generated during the first subperiod and the second subperiod, respectively, should be xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d, xe2x80x9c2xe2x80x9d and xe2x80x9c1xe2x80x9d, xe2x80x9c0xe2x80x9d and xe2x80x9c2xe2x80x9d and xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d, respectively, in the order in which the cylinders are to be controlled.
In a yet further mode for carrying out the present invention applied to a six-cylinder internal combustion engine in which the ignition control period for each of the cylinders is so set as to correspond to a crank angle of 120xc2x0, the plural subperiods should preferably be comprised of a first subperiod and a second subperiod, wherein numbers of the specific pulses contained in the cam pulse signal generated during the first subperiod and the second subperiod, respectively, should be xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d, xe2x80x9c2xe2x80x9d and xe2x80x9c0xe2x80x9d, xe2x80x9c1xe2x80x9d and xe2x80x9c2xe2x80x9d, xe2x80x9c0xe2x80x9d and xe2x80x9c2xe2x80x9d, xe2x80x9c1xe2x80x9d and xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d, respectively, in the order in which the cylinders are controlled.
In a still further mode for carrying out the present invention applied to a three-cylinder internal combustion engine in which the ignition control period for each of the cylinders is so set as to correspond to a crank angle of 240xc2x0, the plural subperiods should preferably include a first subperiod and a second subperiod, wherein numbers of the specific pulses contained in the cam pulse signal generated during the first subperiod and the second subperiod, respectively, should be xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d, xe2x80x9c2xe2x80x9d and xe2x80x9c0xe2x80x9d, xe2x80x9c1xe2x80x9d and xe2x80x9c2xe2x80x9d, xe2x80x9c0xe2x80x9d and xe2x80x9c2xe2x80x9d, xe2x80x9c1xe2x80x9d and xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d, respectively, in the order in which the cylinders are controlled.
Owing to the features described above, there can be realized the cylinder identifying system which can ensure the fail-safe function while enabling the fuel injection control and the ignition control for each engine cylinder to be speedily carried out upon engine starting operation.
In a further mode for carrying out the invention, the crank angle pulse signal should preferably be comprised of pulse trains each of a period corresponding to a crank angle of 10xc2x0, wherein the reference position included in the crank angle pulse signal should be set at a crank angle of 35xc2x0 from the top dead center on a cylinder-by-cylinder basis.
With the arrangement described above, the fuel injection control and the ignition control can speedily be carried out for each of the engine cylinders while ensuring enhanced controllability and high control accuracy.
The above and other objects, features and attendant advantages of the present invention will more easily be understood by reading the following description of the preferred embodiments thereof taken, only by way of example, in conjunction with the accompanying drawings.